On the terminals of electric motors that are used together with electronics (children's electric cars, etc.), you can see one or three capacitors. One capacitor is installed in parallel to the motor power supply, and the other two are installed between the motor body and one of the terminals. In this article, we will see why this is done.
I applied power to the engine and disconnected all the capacitors. I connected the oscilloscope probe between one terminal of the engine and the housing. As you can see, there is interference on the engine housing.
Now I connected one ceramic capacitor with a capacity of 0.1 μF between the motor output and the case and the interference disappeared. The capacitor suppressed this interference.
Next, I check the interference in the electric motor power supply circuit, first without the capacitor. The screen shows surges in the form of vertical stripes, which will be fed to the power supply.
With a 1 μF capacitor installed in parallel with the motor terminals on the power supply, there will be no interference.
Such capacitors for electric motors are mainly used where both the electric motor and electronics are connected to one power source. Microcircuits, microcontrollers and other electronics are sensitive to various types of interference, including those that will go through the power supply. Interference can cause incorrect operation of electronics and to prevent this from happening, interference suppression capacitors are installed.
The efficiency of the capacitors can be checked with a radio receiver tuned to medium waves, installed near the motor power cable. Without capacitors, interference will be heard in the radio reception, with capacitors the interference will be suppressed
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